This is an introduction to, and an overview of, the Space Programming Language Machine (SPLM), which is an architecture for a class of machines designed for efficient execution of on-board, aerospace computation functions. It directly executes software written in the SPLM Language (SPLML), which has been specially constructed as a complete, concise notation for the application area. The goal of the SPLM development effort is to design machines that are smaller, faster and easier to program than currently available aerospace computers. The specific features and characteristics of the SPLM may have general applicability, although this was not a design criterion.